Various types of rotary transducers are known for a variety of applications including printing. Such transducers are also known as stepping motors for a wide variety of functions. In general, electromagnetically operated rotary transducers comprise an even number of poles. Most rotary transducers, however, particularly those used in printing and numbering applications are mechanically operated.
Various types of numbering apparatus are known in the printing art. These are mechanical devices and are operative mainly for sequential numbering of documents being printed. Particular printing wheels are available for such apparatus for printing predetermined sequences of numbers or skipping predetermined numbers, but these also operate only in a predetermined order, since each wheel is rotated by an adjacent wheel.
Examples of conventional mechanical numbering apparatus can be seen in the catalogs of Zeiser K. G. of Bogenstrasse 6-8, Emmingen 1-W. Germany and Atlantic Numbering Machine Corporation of 1333-60th Street Brooklyn New York, U.S. Numbering apparatus of this type suffers from the disadvantages arising of its limitation to fixed order stepwise operation. Among these disadvantages are the requirement that a mechanical trigger be provided in association with the printing apparatus for operating the stepping cam of the numbering apparatus. Difficulties arise in initial set up of the numbering apparatus to a selected non-zero starting number or in resetting the numbering apparatus in the event that some numbered sheets in the middle of the sequence become spoiled and must be reprinted. Both of these operations involve the waste of considerable time in the use of conventional numbering apparatus.
Using conventional numbering apparatus there is no possibility of providing random number printing or printing of random check digits. A further disadvantage is that using conventional numbering apparatus a printing establishment must maintain a stock of a large number of printing wheels to suit particular predetermined sequences of numbers or symbols as well as spare parts for the mechanical portions of the apparatus which are subject to wear.
Numbering wheels and cylinders are also known in desk-top calculators. These generally fall within two groups, one in which the digits are printed by individual hammer action, for example, rather than in a single hammer action and the other in which slow pre-positioning and alignment of the digits take place by mechanical action and printing occurs simultaneously therewith. The functions characteristic of both groups render this type of printing wheel unsuitable for general printing use. In addition, such numbering wheels, notwithstanding their capability, in principle, for random numbering, are too slow and not sufficiently accurate in positioning for general printing use.